Hi.
I have jump started my car with AA batteries before, but now I want to try and see if I can jump start with supercapacitors or supercaps.
As we know, capacitors hold electric charge like a battery.
What's so super about these?
This is a 100 millifarad, 6.3 volt electrolytic capacitor, but this is a supercapacitor rated for 2.7 volts, and it is 400 farads!
(Outside voice) Stop yelling at the camera!
Sh*t.
So, at the same voltage, this supercap can hold 4000 times more charge compared to this electrolytic cap.
Can you digest that? Of course not. It's filled with with chemicals.
But that's a lot of charge for a capacitor, that is. Still, this AA battery can hold 20 times more charge compared to this supercap.
The upside? The supercap has a much smaller series resistance of 3.2 milliohms compared to a typical AA battery, which is around 200 milliohms.
So if I charge this to 2.13 volts and short it, it can deliver up to 666 amps of current.
Coincidence? I think not. Because the current is equal to voltage divided by resistance.
Let me charge it and short it.
I'll charge this cap with a fixed 10 amps from my power supply.
Bluhuhuh! Ha ha ha! You thought the cap was gonna blow, oh no no no! Sir, these expensive, I careful! (kiss)
I scope the voltage and for the fixed 10 amp current, the rate of voltage rise is around 25 millivolts per second.
OK. Let's first short the AA battery and see how much current it can deliver.
9.6 amps.
Now, let's short the supercap.
Of course the resistance of this wire is gonna limit the current through the supercap.
Oww! Sh*t! F*ck!
Sh*t! I totally burned my finger!
The clamp registered 376 amps and we still have 2.2 volts on the supercap.
I think we are on the right track for the jump start.
The downside of the supercaps is that they are generally rated for low voltages like 2.7 volts.
So in order to increase my capacitor voltage, I have to put 6 of them in series in a bank to bring my voltage up to a maximum of 16.2 volts.
But that means that my total capacitance will drop by 6 times to 66.6 farads.
And I have to use high gauge wires to solder them together to make sure...
ooh sh*t
Never solder when your capacitor is charged. It could damage the capacitor or the circuit.
I'm gonna discharge the capacitor with a low gauge wire to limit the current.
Wow! This thing can deliver!
Done. Now let's charge this capacitor bank to 14 volts like a fully charged battery.
Supercaps have high leakage current.
This one is around one milliamp that will drain the capacitor in around 13 days.
I still have lots of time.
First, I'm going to measure the normal current draw of the crank motor from the battery, and I'm gonna use my current clamp and connect it to my scope.
First I have to set up a spot for my scope so it doesn't get dirty.
(kiss)
There will be a Keysight scope giveaway at the end of the video.
My assistant here will help me demonstrate a point while I crank the engine.
You hold on to the battery contacts while I crank the car. And we measure the current on the screen.
[car starts]
@#$%!
Let's try again.
[car starts]
Are you okay?
Yes.
You can see here that the inrush current into the crank motor is around 750 amps, and quickly drops to around 200 amps while we are cranking the car.
When the car starts, it charges the battery, here, so that the current goes to negative 30 to 40 amps.
Now if we look at the battery voltage we see that it starts around 12 volts, and when there is the inrush current,
the voltage drops to 8 volts, and goes back up to around 11, and then when the car charges the battery, the battery voltage goes to 14 volts.
So as I suspected, even if you hold on to the wires that carry a lot of current, you won't be electrocuted.
So you weren't sure?
Ow! You little...
Of course I was 100 percent sure, because the voltage across the body is very small.
Now I disconnect the battery positive to replace it with the capa...
Dogsh*t!
I have to remember not to short the battery.
Now I connect the capacitors to the power lines with these clamps...
Let's crank.
[car starts]
Done! Perfect!
Seems like the capacitor bank is good for one crank, as you can see the current jumps to 450 amp, and then quickly drops to 150 amps.
And also the voltage drops a lot.
You see here that uhh...from 14 volts almost, it drops to around 6 volts and then goes back up.
Of course it charges quickly back up to 14 volts as soon as the engine starts going.
So this can crank a car.
So I have a new Keysight scope.
It's like somebody took God and shoved him into a plastic box and gave him a touch screen too.
It's oozing with power. It's a 1 gigahertz four channel scope, a 16 bit digital analyzer,
an arbitrary waveform generator, an 8 digit frequency counter, and more.
Wowwww!...
(outside voice) Stop yelling...sshhh
Now, I have a brand new lower model Keysight scope with most of the same features that I don't need since I have this one.
So I'm going to give that one away to my supporters at Patreon.com as an ongoing token of appreciation.
If you want to know how scopes work though, that's not what I do.
But you can find very good information in the Keysight Oscilloscopes YouTube channel.